Potential equalization for a metering pump

ABSTRACT

Metering pump having a stationary portion and a pump portion, which is mounted in a linear manner and can be moved relative to the stationary portion in order to move a displacement body, wherein, for the purpose of achieving a long service life, the pump portion is connected in an electrically potential-equalizing manner to the stationary portion via an electrically conductive spring element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to DE Application No. 10 2022 115 557.9 filed Jun. 22, 2022, the disclosure of which is hereby incorporated in its entirety by reference herein.

TECHNICAL FIELD

This invention relates to a metering pump having a stationary portion and a pump portion, which is mounted in a linear manner and can be moved relative to the stationary portion. The pump portion can be used to move a displacement body, in particular a pump diaphragm.

BACKGROUND

The invention falls within the technical field of metering pumps. Metering pumps are used for measuring out amounts of fluid and are generally in the form of positive-displacement pumps. One variant is the diaphragm pump, which often comprises a pump diaphragm made of a non-electrically conductive elastomer as part of the pump portion. Many metering pumps have a drive for producing an at least approximately linear movement of the pump portion. In some embodiments, the pump portion is guided in a linear manner along one or more other components, wherein this guide means is often lubricated with electrically insulating lubricant. During operation, the pump portion can float on the lubricant, which can result in the entire pump portion becoming electrically insulated.

Electrostatic insulation is also possible if, as an alternative, lubricant-free sliding guides are used, in which one friction partner is a plastics material with a low coefficient of friction, for example. In both cases, the movement can also produce electrostatic charging between the stationary portion and the pump portion. This results in a configuration in which electrical flashovers and thus sparks may be produced. In explosion-protected areas, a metering pump of this kind can constitute a serious hazard. Furthermore, it is possible for flashovers to damage the guide means or other components. Therefore, measures are generally taken to prevent electrostatic charging.

It is conceivable to achieve electrical potential equalization between the pump portion and the stationary portion by way of a flexible cable, which creates an electrical short circuit between the two portions. However, especially with a view to durable construction, a cable of this kind has the disadvantage that it may break after a number of movement cycles. Moreover, corrosion may occur between the cable and the components that it electrically contacts during the course of the service life, which may impair the potential equalization.

It is also conceivable for a slider, which slides on the pump portion or the stationary portion, to be provided in order to bring about potential equalization. However, a disadvantage of this solution is that a slider has a limited service life owing to abrasion and moreover the abrasion can have disadvantageous effects.

SUMMARY

The object of the invention is therefore to propose a metering pump that is reliable, durable and suitable for explosion-protected areas.

The subject of the invention is a metering pump in which the pump portion is connected in an electrically potential-equalizing manner to the stationary portion via an electrically conductive spring element.

The dependent claims relate to preferred embodiments of the invention.

In one embodiment of the metering pump, the pump portion is designed to move in a purely translational manner. One advantage of this is, for example, that a pump diaphragm can be moved exclusively normal to a plane in which it extends, which in turn, owing to uniform deformation, enables improved metering accuracy. For example, a linear guide means may be used, in particular a linear guide means wherein the pumping portion is guided between two guide elements or guide portions of the linear guide means.

In one embodiment, the metering pump has a pump drive, which is in the form of a linear drive.

The linear drive may be in the form of a linear motor having a linear stator with a plurality of magnetically active units, which are in particular arranged behind one another in the guiding direction, and an associated rotor, which is likewise magnetically active. The rotor forms part of the pumping portion and is in particular designed to drive the pumping portion. Alternatively, the linear drive may have a spindle for moving the pump portion. In particular, this spindle may be coupled via a thread to a feed element that operates in a linear guide means. In this case, the feed element forms part of the pumping portion and in particular drives the latter.

In one embodiment, one end of the spring element can be in mechanical and electrically conductive contact with the stationary portion. Alternatively or additionally, one end of the spring element can be in mechanical and electrically conductive contact with the pump portion.

In one embodiment, the spring element is in the form of a helical spring. A helical spring achieves a moderate contact force at the same time as a relatively long spring travel and can therefore result in a greater displacement of the pump portion relative to the stationary portion without losing contact, becoming mechanically overloaded or exerting large forces on the pumping portion. The setup is also compact. A helical spring is therefore particularly well suited to this task. As an alternative, it is conceivable for use to be made of a bent wire, which undergoes varying degrees of bending as a result of the movement of the pump drive.

In one embodiment, the helical spring is arranged around a portion of the pump portion. An arrangement of this kind is particularly space-saving.

In one embodiment of the metering pump, the spring element is arranged in such a manner that its spring force assists the pumping force required for generating pressure when pumping by virtue of the spring element being relaxed when pressure is built up. In this way, load peaks for a drive of the pump portion can be reduced during the pumping operation. It may be sufficient for the spring force to act in a direction that differs from the direction of the pumping force. Partial assistance may nevertheless be achieved if there is a proportion of the spring force in the direction of the pumping force.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are shown by way of example in the figures, in which:

FIG. 1 shows a cross section through a first embodiment of the invention, and

FIG. 2 shows a cross section through a first embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 shows a first embodiment of the invention in cross section.

The metering pump 1 comprises a pump head 2, which is inserted into a housing 62 of the metering pump 1. The pump head 2 comprises a displacement body 23. The displacement body 23 is part of a pump portion 3. The pump portion 3 also comprises a drive rod 43. The latter can be driven by an electromagnetic linear drive 4 and moves in a linear manner during operation. The linear drive 4 also comprises a stator 46, which is connected to the housing 62. In the present embodiment, a rotor of the linear drive 4 is formed by the drive rod 43. The stator 46 is connected to the housing 62 of the metering pump. The linear drive 4 can be electrically connected via an electrical connector 45. The pump head 2, the stator 46 and the housing 62 form at least part of a stationary portion 6 of the metering pump 1, which can be moved relative to the pumping portion 3.

The metering pump 1 also comprises a spring element 7, which is in the form of a helical spring in the present embodiment. The spring element 7 is arranged between the housing 62 and the drive rod 43. This arrangement produces an electrical connection between the stationary portion 6 and the pump portion 3, as a result of which potential equalization and suitability for explosion-protected areas can be achieved. The drive rod 43 and the housing 62 are designed to be electrically conductive at least at the point of contact with the spring element 7. For example, the drive rod 43 and the housing 62 can be or comprise metal components.

FIG. 2 is for the most part identical to FIG. 1 , wherein the same features are designated by the same reference signs. No specific description of these features is given. Reference should be made to the description of FIG. 1 .

One difference from FIG. 1 is the arrangement of the spring element 7. In FIG. 2 , the spring element 7 is arranged between a supporting device 47, which is fastened to the drive rod 43 and is in the form of a disk in FIG. 2 , and the stator 46 of the linear drive 4. The supporting device 47 is preferably designed to be electrically conductive, for example is made of metal.

Both in the illustration of FIG. 1 and in FIG. 2 , the drive rod 43 moves downward when the metering pump 1 generates pressure. In both of the embodiments shown, this movement is assisted by the spring element 7, which relaxes during this movement. This reduces the force generation requirements placed on the linear drive 4. 

What is claimed is:
 1. A metering pump having a stationary portion and a pump portion, which is mounted in a linear manner and can be moved relative to the stationary portion in order to move a displacement body, wherein the pump portion is connected in an electrically potential-equalizing manner to the stationary portion via an electrically conductive spring element.
 2. The metering pump according to claim 1, wherein the pump portion is designed to move in a purely translational manner.
 3. The metering according to claim 1, wherein the metering pump has a pump drive, which is in the form of a linear drive.
 4. The metering according to claim 1, wherein one end of the spring element is in electrically conductive contact with the stationary portion, and one end of the spring element is in electrically conductive contact with the pump portion.
 5. The metering pump according to claim 1, wherein the spring element is in the form of a helical spring.
 6. The metering pump according to claim 4, wherein the spring element, in particular the helical spring, is arranged around at least part of the pump portion.
 7. The metering pump according to claim 1, wherein the spring element, in particular the helical spring, is arranged in such a manner that its spring force assists the pumping force required for pumping by virtue of the spring force acting at least partly in the direction of the pumping force.
 8. The metering according to claim 2, wherein the metering pump has a pump drive, which is in the form of a linear drive.
 9. The metering according to claim 2, wherein one end of the spring element is in electrically conductive contact with the stationary portion, and one end of the spring element is in electrically conductive contact with the pump portion.
 10. The metering according to claim 3, wherein one end of the spring element is in electrically conductive contact with the stationary portion, and one end of the spring element is in electrically conductive contact with the pump portion.
 11. The metering pump according to claim 2, wherein the spring element is in the form of a helical spring.
 12. The metering pump according to claim 3, wherein the spring element is in the form of a helical spring.
 13. The metering pump according to claim 4, wherein the spring element is in the form of a helical spring.
 14. The metering pump according to claim 5, wherein the spring element, in particular the helical spring, is arranged around at least part of the pump portion.
 15. The metering pump according to claim 2, wherein the spring element, in particular the helical spring, is arranged in such a manner that its spring force assists the pumping force required for pumping by virtue of the spring force acting at least partly in the direction of the pumping force.
 16. The metering pump according to claim 3, wherein the spring element, in particular the helical spring, is arranged in such a manner that its spring force assists the pumping force required for pumping by virtue of the spring force acting at least partly in the direction of the pumping force.
 17. The metering pump according to claim 4, wherein the spring element, in particular the helical spring, is arranged in such a manner that its spring force assists the pumping force required for pumping by virtue of the spring force acting at least partly in the direction of the pumping force.
 18. The metering pump according to claim 5, wherein the spring element, in particular the helical spring, is arranged in such a manner that its spring force assists the pumping force required for pumping by virtue of the spring force acting at least partly in the direction of the pumping force.
 19. The metering pump according to claim 6, wherein the spring element, in particular the helical spring, is arranged in such a manner that its spring force assists the pumping force required for pumping by virtue of the spring force acting at least partly in the direction of the pumping force. 